A wild guess here.a) They don't have stamina to cross large bodies of water and then drop into it,b) Because they fly in erratic directions and not in a strait line (to avoid being caught) they land in the water and can't escape.

I remember reading about this some time ago. Doesn't it have something to do with the reflection of light on the water, which confuses an insect into thinking that the sky is actually where the water is? If the sky is now in the wrong place, the poor little insect will flip itself upside-down to correct for this, and so fall into the water. Once it comes into contact with the water's surface tension, it is very difficult for it to extricate itself. I think that this can happen both at night and in the daytime, as long as there is a reasonable reflection on a body of water.

Last edited by onewithnature on Wed Aug 22, 2012 1:19 am, edited 1 time in total.

Why do dung beetles roll their balls obsessively in a straight line, even pushing it over obstacles in the way (even though considerable energy may be wasted by so doing) rather than navigating around the obstacle?

Thank you answering Roan. Yes, there is indeed the factor of getting as far away from the competition as quickly as possible. However, there is another reason why they move in a straight line; it doesn't make sense to struggle over an obstacle for a protracted period while the competition is catching up - why not just go around the obstacle?

Rosemary, the pushing backwards does help to keep the ball in a straight line, as well as increase leverage, but there is one particular thing that the beetles use to keep themselves in a straight line.